AR piston versus DI - an honest debate

[tuj]

Alright fellow shooters, I know we've been over this topic before, and I know it comes up ad-infinitum on the AR forums. But I'm looking for some intelligent debate based on a couple of factors here.

We can all agree that the DI current issue M4 is a fairly reliable weapon I think, properly maintained and used with proper ammo. Now since most of us are in the civilian AR family, we get builds and guns of various quality. For purposes of this debate, let us consider only higher-end guns.

Now I know some of the DI guys (of which I am one) will say they have never had a malfunction. I don't have tons of rounds through my AR's like might be put in during a carbine class, but I have never had any malfunctions.

Now I notice a lot of manufacturers are using piston systems. These seem to be better than the piston-kits that were offered for builders and suffered from carrier-tilt.

Of particular note, is that the SOCOM units are now using the HK416, which is a piston-design evolution of the Stoner rifle (at least that's how its been described to me, please correct me if I am selling the 416 short in its design). The primary question is, if piston systems are not superior when masterfully constructed, why are the top operators using them when they have free reign to carry whatever they want?

There seems to be talk that the next evolution of the Army's main infantry rifle will be a piston design. I know this is a perennial topic as well, but the piston design seems to be in favor amongst manufacturers.

Therefore I ask the question: if you need an absolutely dead reliable carbine, do you go with a factory piston system or DI?

 

[Ian]

If you can't articulate specifically why a piston system will work better for your particular application, then you don't need one. DI is the better option for the vast majority of people, and only a few specific niches are better served by a piston.

 

[tuj]

Ian: can you elaborate on when a piston system would better serve its operator?

 

[barnetmill]

I say it depends. I prefer a DI design that has through time had the bugs worked out of it then a newer less tested piston design. Highend DI AR designs are inherently more accurate reaching to sub 1 MOA easily. For a light infantry rifle the DI may have less recoil, but heat up faster during FA. The squad level automatic rifle intended for high volumes of fa I want the piston design. If I go to the 5.56 cartridge I will chose the AR15 since it is ubiquitous and parts and gunsmithing knowledge of it are readily available. It can be used in NRA highpower matches which may not be true for other designs.

For other systems: Roller lock is another option that one can consider. Right now for me I am .30 cal with ak, sks, m1, m14, and now PTR91. Any well established military design that is made to spec will be fine for a civilian.

 

[powder]

Just going on what you wrote, you may have something to add here....

Military units, very specialized Mil units are using suppressors. IIRC, the blowback on a piston unit with suppressor, is much less and advantageous.

So, if your daily AR use will include a suppressor go with the pistons. I just chose a DI AR-10 over the SIG 716, to save about $400 to put towards a decent can. Friends have several of the SIG piston ARs and love them.

Perhaps someone with sandbox time can chime in.

 

[Ian]

The main advantage to a piston, like powder says, is when using a suppressor. That will significantly increase the amount of gas blown back into the shooter's face, and a piston does a lot to alleviate that.

 

[boricua9mm]

I think it was Larry Vickers who said that pistons crammed into the AR make sense for suppressed fully automatic rifles with shorter barrels.

I don't run any suppressed 5.56 weapons, only 9mm and .22LR hosts. I also don't own an machine gun, Lightning Link or RDIAS. For me it would be a waste of money.

Lots of folks seem to think they run "cleaner." I tend to notice that those people are not cleaning and maintaining the gas systems. Eventually when they do open them up, its quite a revelation. "So THAT'S where all the crud goes...."

 

[Quentin]

... There seems to be talk that the next evolution of the Army's main infantry rifle will be a piston design. I know this is a perennial topic as well, but the piston design seems to be in favor amongst manufacturers...

While we can't predict well into the future (the next design could be a phaser as far as we know), at least we know THIS year's Army tests concluded that a piston rifle for general issue offered little to no improvement over the current M4/M16. Comparing new factory-tuned piston designs against used M4s, the reliability rate was something like 99+% vs. 99+%. Sure, some pistons had slightly better results but when you're already at 99% does an extra 0.1% justify replacement expense when that money can be better used for the troops.

As far as manufacturers, they're always happy to convince you to replace the old with "new and improved". That's why every gun rag is hyping piston designs, advertisers are hoping to separate you from your money.

 

[Markm87]

I run short SBRs with Silencers all the time. ALL DI. On some days I'll get a whiff of gas... but it's hardly worth taking on all the reliability issues of the piston nightmare.

Replacing a stainless gas tube with moving parts and springs is retarded on face value..... let alone all the problems like carrier tilt and ammo pickyness that go along with most systems I've seen.

 

[jim243]

Pistons are no advantage to me, just additional cost and repairs.

Jim

 

[Fishbed77]

There seems to be talk that the next evolution of the Army's main infantry rifle will be a piston design.

FYI - the Individual Carbine competition to replace the M4 with a piston rifle has been cancelled because of the cost of the program and because the piston-operated rifles submitted failed to meet reliability requirements. The new carbine had to represent a superior improvement in terms of reliability over the M4 to justify its replacement, not a small improvement:

http://en.wikipedia.org/wiki/Individual_Carbine

Essentially, the switch to a piston-operated rifle just didn't represent an acceptable return-on-investment in terms of cost or reliability over the DI M4.

Of particular note, is that the SOCOM units are now using the HK416

This has more to due with the ease of suppressing piston-operated rifles versus DI, rather than reliability concerns. For units that run suppressors on a pretty-much full-time basis, piston operation makes a lot of sense. For your average infantryman, not so much.

 

[MistWolf]

All a so-called "piston" upper does is move the piston from the carrier to the gas block. The piston in the gas block has less surface to deal with more heat than the piston in the carrier.

I stick with the original gas system in the AR because of cost. Piston-in-gas-block uppers cost more and offer no real advantage, especially after some of the new developments in SBR tuning that's been going on.

I know of a guy in the Norwegian Army using the HK416. He says it's the best rifle he's used for the conditions he's trained in

 

[Bubba613]

Therefore I ask the question: if you need an absolutely dead reliable carbine, do you go with a factory piston system or DI?

I'll note there is no such thing as an "absolutely dead reliable carbine."

Given that most ARs are kept in safes indoors, taken out and shot maybe once a week at most at a range or farm, cleaned, oiled and put back in the safe, they will all work reliably under those conditions.

Anything else is people fooling themselves and gun makers/sellers trying to make money.

 

[JustinJ]

"Pistons" in the general sense can not be compared to DI in terms of reliability and other characteristics because there are quite a few different ones. LWRC makes incredibly high quality guns that are very reliable. However, they also use nickel plating on internals and have excellent quality control. So one can't take that brand and use it's performance as indicative of pistons on the whole. For that matter, which DI gun are we talking about? A variety of different tweaks have been implemented by different manufacturers. There are also varying degrees of quality.

Also, in what conditions are we speaking? One piston gun may do better in highly humid environments than an M4 but worse in sandy. A piston gun may be less impacted by high round count but perform poorer when less than 400 rounds are fired. One may do better than the other based on the rate of fire.

 

[Warp]

If you can't articulate specifically why a piston system will work better for your particular application, then you don't need one. DI is the better option for the vast majority of people, and only a few specific niches are better served by a piston.

Bingo

 

[C-grunt]

Like was stated above, Larry Vickers says a piston is a good idea when you have short barreled, full auto, suppressed guns. Also most of SOCOM doesn't use the 416. Most use some variant of the M4. My one SF buddy uses a Mk18 and the other used a M4A1.

The standard M4/M16 is a very reliable weapon. All you need to do is keep it oiled. It doesn't have to be clean just oiled. My personal Colt sees fairly high round counts per year, except this last year, and I hardly ever clean it. It gets shot suppressed a lot too. I just oil it every month or so.

 

[Slamfire]

Direct impingement makes for an outstanding target rifle. It is however, too dirty for a combat weapon. If the weapon is not cleaned often the propellant residue blown in the mechanism will gum up and cause malfunctions. One common theme of Soldiers coming back from the middle east is how much time and how often they have to clean their rifles.

Compare this to a Korean era veteran I met who told me "no matter how dirty my Garand was, it functioned".

In combat zones, the high maintenance required for DI type actions, where soldiers live in mud and dirt, has eliminated DI from consideration in all but American military weapons. No front line, main battle service rifle, uses DI. It is used by Americans because the Army bought the Colt M16. As long as the Army is wedded to Colt this will continue, but someday there will be a different service rifle and DI will be gone.

 

[Warp]

Direct impingement makes for an outstanding target rifle. It is however, too dirty for a combat weapon. If the weapon is not cleaned often the propellant residue blown in the mechanism will gum up and cause malfunctions. One common theme of Soldiers coming back from the middle east is how much time and how often they have to clean their rifles.

Compare this to a Korean era veteran I met who told me "no matter how dirty my Garand was, it functioned".

In combat zones, the high maintenance required for DI type actions, where soldiers live in mud and dirt, has eliminated DI from consideration in all but American military weapons. No front line, main battle service rifle, uses DI. It is used by Americans because the Army bought the Colt M16. As long as the Army is wedded to Colt this will continue, but someday there will be a different service rifle and DI will be gone.

I don't think so.

 

[Fishbed77]

Direct impingement makes for an outstanding target rifle. It is however, too dirty for a combat weapon. If the weapon is not cleaned often the propellant residue blown in the mechanism will gum up and cause malfunctions.

Real-world testing and use says otherwise.

http://www.slip2000.com/blog/s-w-a-t-magazine-filthy-14/

In combat zones, the high maintenance required for DI type actions, where soldiers live in mud and dirt, has eliminated DI from consideration in all but American military weapons. No front line, main battle service rifle, uses DI.

Pure baloney.

Some 50+ nations use direct impingement M16s, M4s, and variants (Canadian C7, C8, etc.) in front-line use.


.

 

[Gordon]

The op rod on AR type piston guns looks fragile to me and nothing like the AK, which may be superior in reliabilty. I find the guys who have have the latest hi speed mostess usually lack quality training and try to buy ability rather than learn it.

 

[mr.trooper]

I never had a problem, even with low end ARs, wolf ammo, and off-brand magazines, and infrequent cleaning combined.

I don't think DIs have any issue at all - MAYBE if you're shooting 1,000 rounds a day prone in testing sand. Here in North America?

 

[kwguy]

They both work fine, they just each have their 'differences'. Dedicated DI guns work well, but they are just dirtier, and need more lube to keep running when used and abused. But if it's a quality DI gun, it will keep running.

A dedicated piston gun, whether it's a long stroke (AK'ish design) or short stroke piston, works well too. It seems that the crux is whether or not the weapon was designed from the start that way, and not retrofit from DI to piston.

SOCOM are not the only ones using piston 'AR'ish' derivatives. The Marines are also using the HK416. They have both the SAW and the HK416. I don't know if that weapon is meant to complement, or replace the SAW, but it seems to work. Then again, the 416 was designed from the beginning as a piston gun. I think that's the real crux.

I like both designs, but I do indeed find the piston guns to be cleaner and cooler operating; but like someone mentioned earlier, that piston definitely has to be cleaned. And that gas block does indeed get hot. Just not at the reciever.

 

[dprice3844444]

pistons-more weight,something more to break and notlogistically available in shtf situations.if the government thought they were an improvement,they would be using them.

 

[mljdeckard]

I have a couple of problems with pistons.

They aren't standardized. Different manufacturers are trying to find the 'best' way to do it, and if they haven't yet, I don't dare buy one, because in a few years I will be the only one who has it.

They add weight. (Where I don't WANT weight.)

I still think that DI rifles are perfectly reliable. Particularly running mid-length with clean ammo.

 

[kwguy]

They aren't standardized. Different manufacturers are trying to find the 'best' way to do it, and if they haven't yet, I don't dare buy one, because in a few years I will be the only one who has it.

That is certainly one of the main problems with the 'aftermarket' piston systems that are retrofit to a DI gun.